Distance Vector Routing

Couple weeks ago I talked about routing protocols and in the post I mentioned two routing protocol features distance vector and link state. Although these protocols fundamentally do the same thing by getting information on remote networks they get this information in a different way. For today let’s introduce distance vector routing.

With a distance vector routing protocol, a router learns about a route to a different network (that’s the purpose of a routing protocol) the router only knows the “distance” to get there this is usually called the metric. The router also knows the next-hop router along with the outgoing interface to use when sending a packet destined to that network and that’s it.

You could say that a distance vector protocol does not give a graphical representation of the entire network. Look at the picture below R1 has two routes two the network For distance vector the router chooses the lowest metric if this example was using RIP the routers metric would be using hop count and pick the path with the lowest hop count/metric. So although we have multiple routers between R1 and R3, for R1 it only knows and pretty much only cares about the routers that are directly connected to R1 (the red routers) and those are routers are advertising that they have a route reach to R3 (the network.) Distance Vector Protocol

Which IP Routing Protocols use Distance Vector?

Classless No Yes Yes Yes Yes
Supports VLSM No Yes Yes Yes Yes
Send Subnet Mask No Yes Yes Yes Yes
Distance Vector Yes Yes No * No No

*EIGRP is considered a hybrid routing protocol (Uses the best of both Distance Vector and Link-State protocols) In some Cisco documentation EIGRP is also referred to as an advance distance vector protocol.

That’s my summary of at least Distance Vector routing protocols, there is a lot of other helpful information about distance vector and if you would like to learn simple web search would do. Also check out Cisco.com as they do have this and much more helpful documentation. I hope this information was informative and if you have an idea of the next topic that either deals with ICND1 or ICND2 let me know.


3 thoughts on “Distance Vector Routing

  1. jjrinehart June 20, 2011 / 11:30 pm

    I was reading earlier that you passed the ICND1 and that you would be working on ICND2, how is that going?

    • Ryan June 21, 2011 / 5:52 pm

      I’m getting there, like with everything in life things get in the way but in the end I’ll find time.

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